31415...51413 (301-digits)

This number is a prime.

                                                     3 1415926535 8979323846
2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825
3421170679 8214808651 3282306647 0938446095 5058223172 5359408128 2180495352
7132285055 9064483907 4660328231 5680841289 7607112435 2843082689 9802682604
6187032954 4947902850 1573993961 7914882059 7238334626 4832397985 3562951413

A palindromic prime formed from the reflected decimal expansion of π. Found by Carlos Rivera in 2003.